1. Field of the Invention
The present invention relates to semiconductor wafer processing equipment and, more particularly, to a conductive feedthrough extending from a volume containing atmospheric pressure through a ceramic body into a vacuum chamber, and further relates to a laminated ceramic body with multiple internal electrodes.
2. Description of the Background Art
A semiconductor wafer processing system generally contains a vacuum chamber within which is mounted a wafer support pedestal or susceptor. The pedestal is used to support the wafer within the chamber during processing. The pedestal contains various components which provide heating and/or cooling of the wafer as well as clamping (chucking) of the wafer to retain the wafer in a stationary position upon the pedestal surface. Such clamping is provided by either a mechanical clamp or an electrostatic chuck. Within the vacuum chamber, the space above the pedestal where the wafer is processed is generally maintained at a high vacuum. However, the space below or inside the pedestal is maintained at atmospheric pressure.
For high-temperature processes, such as high temperature physical vapor deposition, the pedestal may sometime be fabricated of ceramic. Heretofore, there has not been a convenient nor practical solution for providing an electrically conductive, yet vacuum sealed, connection through a ceramic pedestal such that electrical current can be passed from the atmosphere side of the pedestal to the vacuum side of the pedestal without violating the integrity of the vacuum.
Therefore, there is a need in the art for apparatus that provides a conductive feedthrough connection through a ceramic body, such as a ceramic pedestal, and a method of fabricating the feedthrough.
Additionally, electrostatic chucks are used to electrostatically attract and retain a semiconductor wafer during processing. In some plasma-based wafer processing operation, radiofrequency (RF) power may be coupled to the electrostatic chuck to bias the chuck in order to provide and/or enhance movement of ions in the plasma in the direction of the wafer during processing. The electrostatic chuck typically includes a ceramic body in which a pair of electrodes resides and upon application of DC voltage to the electrodes, the chuck electrostatically attracts a semiconductor wafer to the chuck according to the Johnsen-Rahbek effect. An electrostatic chuck utilizing the Johnsen-Rahbek effect is disclosed in U.S. Pat. No. 5,656,093 entitled WAFER SPACING MASK FOR A SUBSTRATE SUPPORT CHUCK AND METHOD OF FABRICATING SAME, Burkhart et al. inventors, patented Aug. 12, 1997; this patent is incorporated herein by reference. Further, when the electrostatic chuck is used in high temperature physical vapor deposition of the type noted above, the chuck may be biased by coupling RF power to the chuck. If the electrostatic chuck is RF biased by applying the RF power to electrodes embedded and residing in the semiconductor body, the electrodes and metal feedthroughs to the electrodes must be relatively large and thick to carry the RF power. The metal electrodes and metal feedthroughs carrying the RF power have a different coefficient of expansion than the body of ceramic in which they reside and since the metal electrodes and metal feedthroughs are heated during RF biasing, cracking of the body of ceramic can result, causing destruction of the electrostatic chuck, ruination of a partially processed semiconductor wafer residing on the chuck during breakage, and the need to open the chamber and replace the chuck.
Accordingly, there is a need in the art for an electrostatic chuck comprising a ceramic body having electrodes residing or embedded therein which do not cause ceramic breakage upon the application of RF bias to the chuck and heating of the electrodes.